Veterinarians with large animal practices typically work from their truck driving from one client's ranch to another client's ranch. This requires them to carry all of the equipment necessary to practice medicine and surgery as well as perform diagnostic procedures.
One of the pieces of this equipment is a portable x-ray machine and x-ray film cassettes. This is typically used to examine the limbs and joints of large animals, especially horses. In a purchase examination of a horse, it may be necessary to take thirty or more radiographs of the horse's lower limbs. Each joint is x-rayed from several different angles to obtain a complete picture of the condition and health of the joint. In order to take a radiograph, an x-ray cassette containing the film is held adjacent to the body part being x-rayed. The x-ray machine is then used to shoot x-rays through the body part and into the cassette and film.
There are two types of x-ray cassettes typically used. The first type of cassette is an aluminum cassette which has a thickness of approximately 9/16 of an inch and typically has an area of 8″×10″, 10″×12″, or 14″×17″. In order to use the aluminum cassettes, the x-ray film must be loaded into the cassette while in a photographer's dark room. Use of the dark room is necessary to avoid exposing the x-ray film. Each cassette contains enough film for one x-ray. Therefore, in order to do one purchase horse examination, it would be necessary to have thirty or more aluminum cassettes loaded with film then carried into the barn for exposure.
The vinyl cassette holder or tunnel is a newer version of the x-ray cassette. The tunnel is approximately 13/16 of an inch thick and typically has an area of 8″×10″. When using the tunnel, the x-ray film is loaded into the vinyl cassette in a photographer's dark room. Each vinyl cassette contains enough film for one x-ray. The vinyl cassette is an envelope shaped device which is approximately ⅛″ thick, when loaded with film. The area of the vinyl cassette is approximately 8″×10″. It has a lens located on either side of the film. In using the tunnel, the vinyl cassette containing the x-ray film is inserted into the tunnel. The tunnel holds the lenses against the film to produce a sharp image. The cassette is then held in place while the radiograph is taken. The vinyl cassette containing the x-ray film is then removed from the tunnel and a new cassette containing x-ray film is then inserted into the tunnel so the next x-ray can be taken.
X-ray film cassette holders are known in the art. U.S. Pat. No. 4,542,522 issued to Gilbert L. Blais on Sep. 17, 1985 discloses such a device. These prior art holders allow a veterinarian assistant to hold the x-ray film cassette steady in the appropriate spot without being in the line of fire of the x-ray machine. Thus reducing the assistant's exposure to x-rays.
The x-ray film cassette holder disclosed in the '522 patent secures two opposing corners of the cassette and holds the cassette secure against the adjacent sides of the cassette holder. In order to change cassettes, it is necessary to loosen the members securing the opposing corners of the cassette, remove the current cassette and replace it with a new cassette. Loosening the members requires partially unscrewing a threaded nut. His can become a tedious and time consuming task, especially considering that in a typical purchase examination of a horse, it would require that the cassette be changed thirty some times.
Another example of an x-ray cassette holder is the one disclosed in U.S. Patent Application Publication No. US2002/0039402A1 published on Apr. 4, 2002 disclosing an x-ray cassette holder (the '402 patent application). The '402 patent application discloses an x-ray cassette holder which secures opposing sides of the cassette using a U-shaped channel. The cassettes are changed by loosening a screw holding one of the channels in place and then sliding the channel along the bracket far enough so the cassette can be removed and then putting in a new cassette and sliding the U-shaped channel back in place and re-tightening the screw.
While the prior art may work well with the traditional aluminum cassette which requires that the entire cassette be replaced after each x-ray is shot, the prior art, however, adds unnecessary labor to x-ray taking when using the newer style tunnel cassette. With the tunnel, only the vinyl cassette holding the x-ray film is removed from the tunnel and replaced with a new cassette containing the x-ray film for the next picture. However, with the prior art cassette holders, it is necessary to remove the entire tunnel from the holder, replace the vinyl cassette and then reinstall the tunnel into the cassette holder. This adds unnecessary time, labor and expense.
Often times, the assistant tires of removing and reinserting the cassettes into the x-ray cassette holder. At that point, the assistant may begin holding the cassettes in place while wearing a pair of lead-lined gloves and a lead-lined apron to shield the assistant from the x-ray. This obviously raises concerns of the dangers of exposure to x-rays.